1. Technical Field:
This device relates to stretch wrapping machines that make a unitized package by encompassing a multiple part load by a plurality of usually spiral wraps of stretched film material utilizing the rotation of the load to elongate the film from a restrictive supply source.
2. Description of Prior Art:
Prior Art devices of this type have relied on a variety of different film supply brakes to effectively restrict the film as it is pulled from its supply roll and motor brakes to slow an electric magnetic motor, see for example U.S. Pat. Nos. 4,204,377, Pat. 3,867,806, Pat. 4,232,501 Pat. 3,919,611, Pat. 3,603,875 and U.S. Pat. No. 967,237.
In U.S. Pat. Nos. 4,204,377, 3,867,806, and 4,232,501, stretch wrapped process and devices are disclosed that use a magnetic particle brake; in patent ending in 377, a restrictive means characterized by a brake shoe, brake drum and actuation brake lever as illustrated in patent ending in 806. A particle brake is also used in patent ending in 501.
All of the above aforesaid patents rely on common, well known and commercial heat generating braking apparatus.
In U.S. Pat. No. 3,919,611 a braking device for small motors is disclosed that uses a counter electro-magnetic force generated by the motor.
U.S. Pat. No. 3,603,857 discloses a speed control mechanism for controlling a motor to prevent same from exceeding a predetermined maximum speed of rotation of a revolving door.
In U.S. Pat. No. 967,237 a electric hoist is disclosed that uses a braking effect imparted to the hoist motor by driving same backwards with the armature circuit of the motor being closed upon itself.